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ORIGINAL ARTICLE
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Minimally invasive suture anchor – metallic button construct for acute acromioclavicular dislocations: A functional outcome pilot study in military cohort


1 Department of Orthopaedics, Military Hospital Kirkee, Pune, Maharashtra, India
2 Department of Orthopaedics, Fortis Hospital, Gurugram, Haryana, India

Date of Submission02-Nov-2019
Date of Decision27-Dec-2019
Date of Acceptance17-Jul-2020
Date of Web Publication02-Sep-2020

Correspondence Address:
Vyom Sharma,
Department of Orthopaedics, Military Hospital Kirkee, Pune - 411 020, Maharashtra
India
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jmms.jmms_78_19

  Abstract 


Context: The best technique to achieve the optimum functional outcome in acute acromioclavicular (AC) injuries in young, active patients continues to be a matter of debate. Aims: The aim of this study is to evaluate the functional outcome of a minimally invasive technique for acute AC dislocation in military soldiers. Settings and Design: The study design involves prospective study from 2012 to 2016 at a tertiary care Military Orthopaedic center. Materials and Methods: Patients with an acute Rockwood Type III, IV, and V AC injury were included polytrauma, injury older than 2 weeks or requiring an open reduction, ipsilateral limb, and neurological injuries were excluded from the study. All patients underwent minimally invasive, percutaneous reduction and fixation with a suture anchor–metallic button construct. Patients were followed up at 6, 12, 24 weeks, 1 year, and 2 years postoperatively for radiological and functional assessment (Constant score). Statistical Analysis: Using analytical tests in SPSS software for comparison of coracoclavicular (CC) distance on the injured and healthy sides. Results: There were 25 male soldiers and cadets with a mean age of 24.5 ± 5.5 years. The mean follow-up duration was 37.9 ± 6.26 weeks. Twenty-four (96%) patients achieved pain-free, overhead shoulder abduction at 24 weeks follow-up with a mean constant score of 88.4 ± 7.43. The mean constant score at the last follow-up was 94.5 ± 5.67. Twenty-three (92%) patients had a well reduced AC joint; mean CC distance on the affected side was 9.1 ± 1.2 mm, comparable to mean distance of 8.9 ± 1.4 mm on the healthy side without any evidence of sclerosis or osteolysis till the last follow-up, while one patient had a recurrent dislocation. Conclusions: Suture anchor metallic button construct is a simple, surgeon friendly technique for young, high-demand patients to restore AC biomechanics in a minimally invasive manner.

Keywords: Acromioclavicular injury, minimally invasive, soldier, suture anchor



How to cite this URL:
Mishra AK, Sharma V, Chaudhry A. Minimally invasive suture anchor – metallic button construct for acute acromioclavicular dislocations: A functional outcome pilot study in military cohort. J Mar Med Soc [Epub ahead of print] [cited 2020 Nov 28]. Available from: https://www.marinemedicalsociety.in/preprintarticle.asp?id=294197




  Introduction Top


Acromioclavicular (AC) injuries are a perfect instance of the spectrum of soft-tissue disruption that can present either as an acute episode of painful deformity or a painless significant displacement in a chronic situation. AC disruptions are most commonly seen in males, 30 years and younger, involved in high-demand activities or sports, commonly labeled as “high risk” athletes.[1],[2] The management of these injuries has been described since the era of Hippocrates,[3] and current literature on the management of AC injuries have brought out the essentiality of actively managing these injuries in young, high-demand individuals.[4] The treatment guidelines have been based on the validated and commonly used classification for these injuries, proposed by Rockwood.[5] There has been an evolution of techniques for the management of AC injuries, but no particular technique qualifies as the perfect solution to restore the AC joint biomechanics. Surgical options, including a fixation with pins, tension band wiring, procedures such as Weaver-Dunn, suspensory fixation devices, and clavicular hook plate, have not scored significantly over the other.[4] There is a biomechanical rationale to anatomically reconstruct the coracoclavicular (CC) ligaments, and the last decade has witnessed reports on minimally invasive arthroscopic fixation of AC injuries, including suspensory devices.[6] The minimally invasive technique of realigning the clavicle– coracoid axis and reducing the AC joint with suture anchors has been described with either 3.5 mm anchors[7] as well as a single 5.5 mm anchor technique.[8] The aim of this study was to evaluate the outcome of acute AC dislocations in military soldiers, managed by a simple, more surgeon friendly, and easily reproducible minimally invasive technique using suture anchor – metallic button construct.


  Materials and Methods Top


The study design is a prospective pilot study at a tertiary care Military Orthopaedic center from 2012 to 2016 following Institutional ethical committee approval. The study included all consecutive patients with an acute (<2 weeks) Type III, IV, and V AC dislocation after obtaining written, informed consent. Exclusion criteria were Type I and II Rockwood AC injuries, polytrauma, open injuries, neurovascular injury, ipsilateral shoulder or upper limb trauma, and injuries older than 2 weeks.

All the patients were radiologically evaluated with a series of shoulder radiographs, which included a true anteroposterior view, trauma lateral, Zanca's view, and a comparative stress radiograph for the contralateral AC joint and CC distance measurement. The radiological classification was assigned by one of the authors based on the AC separation, in addition to CC distance measurement on the injured and normal side [Figure 1]. The patients were followed up at 6, 12, 24 weeks, 1 year, and 2 years postoperatively. At each follow-up visit, the clinical evaluation was directed to detect any step in AC articulation and residual tenderness. The radiological assessment at each follow-up included the congruency of AC articulation, placement of the suture anchor in the coracoid process, seating of the metallic button on the superior clavicular surface, any comparative increase in the CC distance or loss of reduction and dislodgement of the suture anchor-metallic button construct. The functional assessment and outcome were done with the Constant–Murley scoring system[9] and categorized in fair, good, or an excellent score. The statistical analysis was performed using analytical tests in SPSS software (SPSS statistical analysis software version 20, IBM Inc) for comparison of CC distance on the injured and healthy side.
Figure 1: Comparative radiograph of a Type III Rockwood acromioclavicular dislocation

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Surgical technique

The operating team comprised the senior author in all the cases. The patient was positioned in a beach chair position after regional or general anesthesia. The AC articulation and clavicle were visualized in the C-arm image intensifier [Figure 2]a before the procedure was started to ascertain the reducibility of the AC dislocation by closed means. The skin was marked over AC articulation, lateral third of the clavicle and acromion. The skin was incised over the junction of lateral third and medial two-thirds of clavicle using a no. Ten surgical blade, about 10–15 mm to expose the superior surface of the clavicle, preferably collinear with an imaginary line connecting the inferior surface of the clavicle and the medial border of the coracoid process. The stab incision was placed in a manner to facilitate a straight trajectory from the superior surface of the clavicle, and the coracoid process and subperiosteal dissection were done to expose the superior surface of the clavicle. A 1.5 mm K-wire was drilled in the center of the clavicle midway from anterior and posterior margins of the clavicle directed postero-inferiorly toward the base of the coracoid process followed by a 4.7 mm cannulated drill over the K-wire to make a hole in the clavicle [Figure 2]b. The use of K-wire as a guide in drilling hole in the clavicle prevented the eccentric placement of the hole. Subsequently, a 5.5 mm preloaded, four-strand titanium suture anchor (Arthrex) was passed through the hole in the clavicle and fixed in the base of the coracoid process [Figure 2]c. The coracoid process is a stout, hook-shaped bone with its apex facing laterally that provides an excellent purchase for the anchors. To avoid eccentric placement of the suture anchor, the medial and lateral surfaces of the coracoid are sounded with the tip of the drill bit and an indentation made in the approximate central area. The position of the suture anchor in the coracoid process was confirmed by C-arm, followed by ascertaining a good purchase of the suture anchor by pulling the threads. The threads of the suture anchor were held through the hole in the clavicle and looped through a titanium open 4 hole button (striped sutures was passed through the inner two holes and white sutures were passed through the outer two holes of the button enabling concentric forces by both the sutures in the direction of native CC ligaments). The fixation over a titanium button helped in better fixation of the clavicle to the coracoid process and prevented slipping of the sutures along the long axis of the clavicle. It also prevented stress riser at the site of fixation by evenly distributing the compressive forces around the drill hole in the clavicle. The AC joint was reduced manually by a distal and downward push on the distal clavicle and a counter-force from the elbow. The reduction was confirmed under C-arm, and simultaneously, the strands of the suture anchor were tightened over the metallic button by sliding knots alternately, ensuring a perfect seating of the button absolutely flush on the superior surface of the clavicle. During this last step, one of the assistants maintained the reduction of the AC joint while the lead surgeon tied the knots over the titanium button [Figure 2]d. We encountered difficulty in a closed reduction in two cases that required the opening of AC joint and excision of the torn meniscal disc for an accurate reduction. These cases were managed by using clavicular hook plate, hence, excluded from the study as they did not fulfill the inclusion criteria.
Figure 2: (a) Type III acromioclavicular dislocation before reduction (b) Drilling of K-wire and drill from clavicle to coracoid process visualized in image intensifier (c) Fixation of suture anchor in coracoid process (d) Acromioclavicular reduction and tying of the knots over the metallic button on clavicle

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Postoperatively, the patients' shoulder was protected in an arm sling pouch for 6 weeks to neutralize the downward pull on the repair due to the effect of gravity on the upper extremity. The patients were allowed intermittent elbow and hand movements in the immediate postoperative period and shoulder pendulum exercises after 3 weeks. At 6 weeks postoperatively, the patient was put through a supervised shoulder rehabilitation program. This included a gradual increase in active assisted abduction and rotations over the next 6 weeks to regain the active range of motion after the sling has been discontinued. However, to avoid excessive stress on the AC reconstruction and failure of fixation, all patients were advised to cautiously increase internal rotation and forward flexion and within the pain threshold till 12 weeks. At 12 weeks, closed chain scapular exercises and kinetic chain activities were commenced with gradual progression up to 24 weeks. All the patients were allowed noncontact sporting activities after 24 weeks and return to contact sports at 9 months postoperatively.


  Results Top


The study included 25 patients after excluding the patients requiring open reduction [Figure 3]. All patients were male, soldiers and cadets involved in high demand physical activities. The mean age of the patients was 24.5 (18–37) ± 5.5 years, and fifteen patients were <30-year-old. Eighteen (72%) patients had Type III, 2 (8%) Type IV, and 5 (20%) Type V Rockwood AC dislocation. The common mechanism of injury was a fall on an outstretched hand or shoulder sustained during sports events in 15 (60%), road traffic accident in six (24%), and fall during military duty in 4 (16%) patients [Figure 4]. Twenty (80%) patients had an injury in the dominant arm. The average time of surgical intervention from the day of injury was 10.7 days (5–14 days). The average duration of the procedure was 35 min (30–55 min), which was about 55 min in the initial cases. The average hospital stay after the procedure was 7 days due to the logistics, as all soldiers have to travel to different parts of the country to join duty or their home town for convalescence.
Figure 3: Flow diagram of study participants

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Figure 4: Mechanism of injury pattern

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The average follow-up duration was 37.9 (26–60) ± 6.26 months. The functional outcome was assessed at each follow-up visit with constant score evaluation. Twenty four (96%) patients achieved pain-free, overhead shoulder abduction at 24 weeks follow-up with a mean constant score of 88.4 ± 7.43. The average constant score at the last follow-up was 93.5 ± 11.7 with an excellent score in 16 (64%), good in 6 (24%), and fair in 3 (12%) patients. Four patients had a full score at the last follow-up. All the patients were able to do full overhead abduction and rotations at the shoulder. The assessment of components of constant score at the last follow-up as depicted in [Figure 5] showed a pain score that was almost normal. The mean score of strength testing lagged behind the range of motion and activities of daily living (ADL) at 24 weeks follow-up that was commensurate with the supervised rehabilitation regime. There was a proportionate escalation in strength scores (22.04 ± 2.25) at the last follow-up, as well as the range of motion (35.5 ± 3.16) and ADL (17.2 ± 2.39) scores. The preinjury activity level was achieved by 1 year postoperatively in all the patients that were evaluated by the ability to perform 5 m horizontal and vertical rope climbing as per the standards of physical training in military soldiers. The radiological assessment at each follow-up included the congruency of the AC joint, position of the suture anchor on scapular Y view [Figure 6], and clavicular button and the CC distance on stress radiographs, which was maintained as compared to the uninjured side. The mean CC distance on the affected side was 9.1 ± 1.28 mm (6.9–11.4 mm), comparable to a mean distance of 8.9 ± 1.23 mm (6.8–11.0 mm) on the healthy side and not significant statistically as shown in [Table 1] and [Figure 7]. There was no evidence of clavicle or coracoid fracture, anchor loosening, AC arthritis, clavicular sclerosis or osteolysis till the last follow-up. One of our patients had a recurrence of AC dislocation at 8 weeks postoperatively when he accidentally lifted his 5-year-old child, resulting in clavicular cut through of the metallic button. He was managed with open reduction and clavicular hook plate fixation.
Figure 5: Constant score component distribution

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Figure 6: Follow-up radiograph shows congruent acromioclavicular joint and anchor position in scapular Y view

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Table 1: Restoration of coracoclavicular distance in injured shoulder on comparative analysis with normal shoulder

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Figure 7: Restoration of coracoclavicular distance compared to uninjured side

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  Discussion Top


The general consensus on supporting nonoperative management of Type I and II Rockwood injuries is based on ample evidence, and nonoperative treatment is the norm in such cases.[10],[11] Similarly, type IV–VI Rockwood injuries are in the ambit of operative treatment.[12] The controversy on operative management of type III injuries has been discussed and brought to the fore, especially in athletes and young high-demand patients.[13],[14]

The spectrum of surgical procedures for the treatment of AC dislocations includes procedures ranging from AC reduction and fixation alone to ligament repair and reconstruction or muscle transfers.[12],[15] The decision to choose any surgical procedure and fixation device depends on its ability to restore and maintain a congruent AC articulation and mimic the biomechanics of the native joint. The earlier results of fixation with pins alone have gone into disrepute now due to complications of breakage of pins and unpredictable pin migration.[12] There has been a rising trend toward the use of a precontoured clavicular hook plate in the past decade. The variability in the use of the hook plate with or without ligament reconstruction has shown decent outcomes, though in very small sample sizes and especially in Type III injuries[13],[16] with concerns such as implant-related subacromial impingement, rotator cuff lesions, and subacromial bursitis.[17],[18]

The amphiarthrotic nature of the AC joint and the rotation of the lateral clavicle on the scapula are the primary determinants to be considered whenever a fixation device is chosen for these injuries. The concept of CC fixation, initially advocated by Bosworth[19] is a biomechanically sound principle since it allows an indirect reduction of the AC joint and provides a strong construct. However, Bosworth's procedure had a distinct disadvantage of the necessity to remove the CC screw after a few weeks to enable overhead shoulder movements and avoid any inadvertent screw breakage. The surgical technique in our series is inspired and based on the biomechanical principle of the Bosworth technique. However, there are a number of modifications in our technique. This technique incorporates CC fixation stabilized on a bipod made by the suture anchor device in the coracoid process and the fiberwire securing the reduction of the AC joint on a metallic (titanium) button over the superior clavicular surface. The advantages of our technique are evident in various aspects of the AC joint reduction. The average incision size in our technique was 10 mm [Figure 8], which is comparable to the arthroscopic technique and much lesser than the conventional open techniques. The most significant advantage of our technique is an indirect reduction of the AC joint. In all the cases, the AC joint was not opened, and the reduction was achieved indirectly. The postoperative rehabilitation in all the techniques focuses on an initial period of protection in an arm sling followed by a staged rehabilitation.[20] In our technique, the shoulder rehabilitation is staged, and since there is no secondary procedure like removal of the implant, the pace of recovery is faster. The average Constant score of about 90 was achieved by all the patients by 1 year follow-up, leading to return to sports and preinjury activity level.
Figure 8: Minimally invasive skin incision

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Arthroscopic assisted (tightrope)[12] fixation of the AC joint has got its merits and demerits. The tightrope technique is a minimally invasive technique with good early results. However, the mid-term results of the tightrope and similar arthroscopic assisted techniques have shown a significant number of cases of loss of reduction in up to half of the cases.[20] In addition, these techniques have a steep learning curve and the cost of the implant is also a factor of concern. The apprehension of the dislodgment of such devices as in the tightrope technique[11] is a major concern. The tip to ensure minimal failure in our technique was a very meticulous drilling of the track for the suture anchor. It was ensured that the suture anchor was seated in the base of the coracoid process in the middle third. Second, the strength of the four strands of the fiberwire was utilized to the maximum by tightening over the metallic button using the sliding knots while the AC joint was perfectly reduced under the image intensifier.

The biggest biomechanical hurdle in fixation of AC injuries is the restoration of an efficient rollback of the lateral clavicle to facilitate the scapulothoracic motion.[21] The strength of the four strands construct of the fiberwire is a very strong construct,[22] comparable to native CC ligament which is approximately 500 N[23],[24] which ensures that the fixation of the AC joint is a semi-rigid construct which allows at the same time an efficient clavicular rollback.

In our study, all the patients were individuals with high-demand physical profile that was a criterion to manage Type III injuries also. The functional and radiological outcome in all the patients has been excellent with one failure due to accidental premature loading. The mechanical efficacy of the placement of suture anchor in the coracoid can be done by limited exposure of coracoid;[22] however, in this study, there was no significant difficulty in obtaining a good fixation point for the suture anchor, guided by the C-arm.

There are certain prerequisites before proceeding with this technique. The results have been studied in an acute presentation because chronic AC dislocations would have significant fibrosis, and just fixing the CC axis would not suffice to enable regaining the full shoulder strength. The technique per se requires meticulous placement of the hole in the clavicle and a perfect tightening of the knots over the metallic button, which requires the additional time which was taken in the first few cases in our study.

The limitations in our study were small sample size and a single technique-based outcome study due to the authors' intention to establish the efficacy of this technique before comparing it with other established techniques in a randomized fashion. There is radiation exposure at various steps of the technique, which can be kept to the minimum by good preoperative positioning of the patient and the image intensifier.


  Conclusions Top


The outcome of this surgical technique for acute AC dislocations has been consistent, and the restoration of shoulder function is excellent without any significant complication. This method is based on the primary natural healing of the ligaments and not on reconstruction. The fixation has only provided internal bracing to promote the healing of ligaments by primary intention. This is a promising, safe, and reproducible technique which will be well appreciated and easily performed by general orthopedic surgeons in peripheral hospitals to avoid delay in treating these injuries. However, this technique requires further validation through a multicentric model in a randomized fashion on a larger sample size of patients to draw comprehensive conclusions for surgical treatment of acute AC injuries.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
 
 
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